With the rapid advance of radio communication technology, the communication system has highly evolved. LTE is one of the promising 4th generation mobile communication technologies. In an LTE system, various techniques are adopted to meet the explosively increasing traffic demands, and carrier aggregation is one of such techniques. The carrier aggregation is used to flexibly expand available bandwidth by aggregating multiple secondary carriers with a primary carrier, unlike the legacy LTE system using a single carrier, between a User Equipment (UE) and an evolved Node B (eNB). In LTE, the primary carrier is referred to as primary cell (PCell) and the secondary carrier as secondary cell (SCell).
Meanwhile, in case that the locations of the eNB apparatuses using the primary and secondary carriers are different from each other due to the deployment of repeaters and Remote Radio Head, it may be necessary to change the uplink transmission timing. For example, when the eNB apparatus configured with the primary carrier and another eNB apparatus configured with the secondary carrier are located at different places, it may cause problem in transmission timing depending on the location of the UE since the uplink signal addressed to the remote eNB apparatus should be transmitted earlier than the signal addressed to the near eNB apparatus. In such case that a plurality of uplink timings for different carriers exists, if the uplink timings are configured individually, this increases uplink transmission delay thus there is a need of reducing the uplink transmission delay.